PSI - Issue 61

Berkehan Tatli et al. / Procedia Structural Integrity 61 (2024) 12–19 B. Tatli et al. / Structural Integrity Procedia 00 (2024) 000–000

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strikingly a ff ects both microstructural evolution and crack propagation mechanisms. It is important to note that the observed anisotropy in the initial hardening stage can be attributed to the limited number of ferrite grains (approxi mately 80) used in the crystal plasticity simulations.

Fig. 3. Phase Field Distribution (Top) and Engineering Stress-Strain Response (Bottom) of VF37-Morpho1-Oriset1 and VF37-Morpho1-Oriset2.

Fig. 3 illustrates the results obtained for 37% martensite volume fraction (vf37) simulations with two di ff erent random crystallographic orientation sets (Ori1 and Ori2). Based on the true stress-strain curve, the material displays a less duc tile response, with cracking occurring at an earlier stage and at higher stress levels, as expected. Stress concentration is more pronounced at the ferrite / martensite interfaces, with further increases in concentrated stress values in the coa lesced martensite grains. Comparing the Von Mises stress contour plots from Fig. 1 and Fig. 2 with Fig. 3, it becomes apparent that as the martensite volume fraction increases, the influence of crystallographic orientation on the stress contours diminishes. Furthermore, the resultant crack paths shown in Fig. 3 demonstrate remarkable similarity across two entirely random crystallographic orientation sets. This suggests that with increasing volume fraction, the influ ence of crystallographic orientation diminishes, and instead, the mechanical response appears to be predominantly governed by the martensite phase itself. This study aims to investigate crack nucleation and propagation in dual-phase steels. Utilizing polycrystalline RVEs, the proposed approach integrates J 2 and crystal plasticity models with a phase field fracture framework to exam ine the influence of microstructural parameters on the failure of dual-phase steels. To achieve this, three-dimensional thin-plate microstructures are generated with varying martensite volume fractions, morphologies, and crystallographic orientation sets and then simulated. The results indicate that for low-volume fraction DP steels, crystallographic orien tation and morphology significantly a ff ect the resultant crack path. Damage tends to accumulate predominantly at the junction points of the martensite islands while following a transgranular path across the ferrite grains, observed in both low- and high-volume fraction DP steels. Moreover, as the volume fraction increases, the impact of crystallographic orientation diminishes, with the martensite phase itself beginning to dominate the mechanical response of the steel. The proposed framework has proven e ff ective in reproducing findings from the literature for dual-phase materials; however, numerical and material parameters should be fine-tuned for further analysis. 4. Conclusions and Outlook